feat: select multiple dates

[christianrank]

The calendar should allow selecting multiple dates independently, not only single values or ranges. Also we want to make it possible to select all days of one weekday or an entire month.

New props:

name	type	default	description
multiple	Boolean	false	make it possible to select multiple values
selectWeekDays	Boolean	false	make it possible to select all days of one weekday, e.g. all sundays
selectMonths	Boolean	false	make it possible to select an entire month

[ant-design-bot]

Deploy preview for rc-calendar failed.

Built with commit 62fbec07934b3c4157a8a41b6982423320266acd

https://app.netlify.com/sites/rc-calendar/deploys/5bdc7690e39e7c5d42e003ee

[3dw1np]

I really hope this feature will be add soon !